Evolution of the socio-hydrological system in the Lower Yellow River under human regulation

The rapid expansion of dam construction highlights the need to understand the impact of human regulation on river ecosystems and surrounding communities. This study focuses on the Lower Yellow River Basin, a region severely affected by water scarcity, flooding risks, and low ecological resilience. The Xiaolangdi Reservoir, completed in 1999, was designed to address these challenges. Through a comprehensive analysis of the reservoir’s effects on downstream hydrology, geomorphology, ecology, and human activities, we evaluate its effectiveness and explore the interaction between natural processes and human interventions. Our findings indicate that reservoir operations have transformed the river channel from a braided to a meandering form, enhancing flood transport capacity by 79%. While sediment scouring has partially mitigated sediment interception, helping reduce coastal erosion in the Yellow River Delta. However, altered seasonal flow patterns have created water shortages for irrigation and environmental flows, exacerbating conflicts between human and environmental water requirements. Riverbed incision has decreased water diversion efficiency, contributing to groundwater over-extraction with depletion rate of -31.9 mm/year. Additionally, Degradation of tidal flats caused by sediment deficiency has threatened migratory shorebirds, with its populations declining by an average of 1,573 individuals annually.  This study also indicate that the influence of hydrological factors is diminishing over time, while local human activities are having a growing impact on the system. To mitigate future risks, we advocate for the adoption of adaptive, localized, and nature-based management strategies, including the restoration of riparian wetlands, dynamic water allocation, and enhancement of delta resilience through hydrological connectivity and living shorelines. This research offers valuable insights for sustainable water resource management in the Lower Yellow River and other regions facing similar issues.